This invention generally relates to vascular catheters and particularly to catheters for vascular procedures such as percutaneous transluminal coronary angioplasty (PTCA).
In typical PTCA procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient and advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guidewire is introduced through the guiding catheter and advanced into the patient's coronary vasculature until the distal end of the guidewire crosses the lesion to be dilated. A dilatation catheter having an inflatable balloon on the distal portion thereof is advanced over the previously introduced guidewire, with the guidewire slidably disposed within an inner lumen of the dilatation catheter, until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, relatively inelastic balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
Further details of angioplasty procedures and the devices used in such procedures, can be found in U.S. Pat. No. 4,332,254 (Lundquist); U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.) U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.); and U.S. Pat. No. 4,616,652 (Simpson) which are hereby incorporated herein in their entirety.
It is generally desirable to make the deflated profile of the dilatation catheter as small as possible because a smaller profile allows a catheter to pass through tighter lesions and to be advanced much further into the patient's coronary anatomy. However, if the diameter of the guidewire is reduced to reduce the profile of the catheter, the ability of the guidewire to transmit torsional and axial forces is likewise reduced. Heretofore, movable guidewires utilized in coronary angioplasty typically have been on the order of 0.012-00.018 inch (0.305-0.457 mm) in diameter. Attempts have been made to use smaller diameter movable guidewires in angioplasty procedures, but such smaller diameter guidewires frequently were unable to effectively transmit torque for steering the guidewire from the proximal to the distal ends, and, in many instances, they did not have the pushability to be readily advanced through the tortuous coronary vasculature without buckling or kinking.
Heretofore, attempts have also been made to reduce the profile of dilatation catheters by reducing the wall thickness of the tubular members which make up the catheters. However, as with reducing the diameter of the guidewire, there is a limit on how much the wall thickness of the tubular members can be reduced without detrimentally affecting the performance of the catheter.
What has been needed and heretofore unavailable is a dilatation catheter assembly which has a substantial reduction in profile with essentially no loss in performance characteristics. The present invention satisfies that need.